I'm fond of commercial Juki or Pfaff or Brother machines. Pfaff moreso as they have had the dual feed dog (beats the walking foot) for a very very long time.
I would suggest a lockstitch variety over a chain stitch. Chain stitch is designed by its very nature to unravel quickly. It's the stitch type used on your livestock feed bags. However, if you use that type, when you go to put your grommets in, make sure they are in such a position as to help stop the chain stitch from fully unraveling.